It is well known in the art that catalytic systems comprising a transition metal compound and an organometallic compound can be used for the low pressure polymerization of olefins. Various proposals have heretofore been made as to improvements of catalysts of this type.
It is known from British Pat. No. 1,140,649 of Oct. 17, 1967, that there can be used as a derivative of the transition metal of the catalytic systems mentioned above, a solid obtained by reacting a halogenated derivative of a transition metal with an oxygenated compound of a bivalent metal such as magnesium. The catalytic systems thus obtained are very active if they are compared with those in which the halogenated derivative of a transition metal is used as it is.
In Belgian Pat. No. 791,676 of Nov. 21, 1972, there are disclosed catalytic systems having one component which is obtained by reacting together:
(a) an oxygenated organic compound of a divalent metal such as a magnesium alcoholate or phenate;
(b) an oxygenated organic compound of a transition metal; and
(c) an aluminum halide.
A polymerization process featuring advantages over processes using conventional catalysts is described in Y. Kondo et al U.S. patent application Ser. No. 501,879, filed Aug. 30, 1974. The solid catalytic complex, used together with an organometallic compound of a metal of Groups I to III of the Periodic Table according to that process, is obtained by reacting together:
(1) metallic magnesium,
(2) a hydroxylated organic compound like monohydric and polyhydric organic alcohols and hydrocarbylsilanols,
(3) an organic oxygenated compound of a transition metal of Group IVb, Vb, or VIb of the Periodic Table, and
(4) an aluminum halide.
This process is able to provide polyolefins having a high impact resistance by using catalysts featuring high activities. However, the molecular weight distribution of the resultant polymers cannot be easily controlled.